Translational motion apparatus

ABSTRACT

A magnesium carriage of inverted-U cross-section having a flat top and two generally triangular sides rides on bearings along a rectangular aluminum rail. One of the sides of the rail includes a shoulder projection, the lower surface of which provides a running surface for a pre-load bearing that operates to distribute the total load among other bearings, two of which ride on top of the rail and three of which ride on the opposite side of the rail shoulder projection. The carriage moves a structure supporting the reading heads of an information storage and retrieval system. A partially hollow rectangular block of the same material as the rail supports the above-described structure.

United States Patent 1191 Pejcha 11] 3,847,454 Nov. 12, 1974 TRANSLATIONAL MOTION APPARATUS [76] Inventor: Ivan Pejcha, 428 Montclair Dr.,

Santa Clara, Calif. 95051 3,526,938 9 1970 Grabher 308 3 R 4,880,673 10/1932 Bath 308 3 R FOREIGN PATENTS OR APPLICATIONS 582,295 7/1933 Germany 308/6 R 277,762 9 1951 Switzerland....; 308/6 R Primary Examiner-Charles J. Myhre Assistant ExaminerR. H. Lazarus Attorney, Agent, or FirnzA. C. Smith [5 7 ABSTRACT A magnesium carriage of inverted-U cross-section having a flat top and two generally triangular sides rides on bearings along a rectangular aluminum rail One of the sides of the rail includes a shoulder projection, the lower surface of which provides a running surface for a pre-load bearing that operates to distribute the total load among other bearings, two of which ride on top of the rail and three of which ride on the opposite side of the rail shoulder projection. The carriage moves a structure supporting the reading heads of an information storage and retrieval system. A partially hollow rectangular block of the same material as the rail supports the above-described structure.

10 Claims, 6 Drawing Figures PATENTEDnnv 12 I974 sum 10F 3 PATENTEUNHV 12 1914 3.847Q454 sum 2 or s TRANSLATIONAL MOTION APPARATUS BACKGROUND AND SUMMARY OF THE INVENTION Certain known information storing and retrieving systems use discs to store large amounts of information in the magnetic material coating covering the surface of a disc. The magnetic field of this material can be reformed in selected locations by an electrical signal delivered by an appropriatetransducer, in a knownmanner. Conversely, this magnetic field can laterbe sensed to reproduce the original signallf the signal represents a piece of information, then the disc surface forms part of an informationstorage andretrieval system.

In order to store a-large amount of information the transducer or reading head must place the information signal on a narrow track on'the disc surface. For this reason, a drive mechanism is required which will place a signal transducer quickly and accurately on a track. Ideally, the drive mechanism'should move the signal transducer linearly, quickly and accurately from the rest position to the narrow track where the information will be stored and from where it will later be retrieved. In practice, however, the movement may be twisted, full of vibrations and overrun-the narrow track. These undesirable movements may result from one or more of Y directions,.thus assuring a linear, vibration-free ride for-thecarriage. Fourth, the magnesium carriage is light-weight, strong, rigid, and requires little power to move and position accurately. Fifth, the carriage has a symmetrical design and substantially embraces the rail,

thus providing good stability for moving linearly along the rail.

the following factors: lack of rigidity of the railon which the carriagerides; or, assymmetrical mass distribution in the design of the carriage; or, poor choice of materials for the rail, base plate, or carriage, for instance, improper choice of dissimilar materials; or, poor raildesign and inadequate positioning of carriage bearings on the carriage itself or on the rail. Thus, it is undesirable, for example, to have a rigid carriage made of heavy solid rectangular blocks, because excessive mass will result in lack of speed, uncontrollable vibrations and require too much'power to move. On the other hand, if the carriage isnot sufficiently rigid, it will have a very low natural frequency and poor servo efficiency, and, as a result, it will be difficult to obtain good servo response.

The present invention employs an aluminum base block and an aluminum rail for supporting a magnesium carriage which transports a signal transducer structure, and also includes means formovingthe carriage on the rail. The base is a partially hollow block. The rail is a rectangular blocksuppor ted by mounting flanges and includes a precisely flat rectangular top, and two precisely flatrectangular sides,.one of which has, however, a shoulder projection tilted atanangle. The sides and top of the rail provide running surfaces for bearings supporting a carriage. Twoof these bearings ride on top of the rail three on one of the sides, and one on the lower surface of the shoulderprojection.

The carriage comprises a flat rectangular top and two vertical sides of generally triangular-shape. These three sides present an inverted-U cross-section from an end view. The carriage is supportedbybearings of which three are attachedto one-ofthesetriangular sides, two are attached to the carriage top, and one, called apreload bearing, is attached 'toan extension arm of the other carriage side. i

The top of the carriagehastwo-slots each of which houses a bearing and is'located in the middle of each of its narrow ends. Bolt holes on the carriage top re- DESCRIPTION OF .THE DRAWINGS FIG. 1 is a view of the base block and of the rail.

FIG. 2 is an end view of the base block and the carriage.

FIG. 3 is aview of the carriage and one of its sides.

FIG. 4 is a view of the slanted carriage side and of the pre-load bearing arm.

FlG.-5.is a view of thepre-load bearing armshowing the eccentric postandithe arm spring.

FIG.- 6 is a view of the voice .coil assembly and magnet.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. .1, the bas e blockl0 is, an aluminum rectangular blockhavjng two equal internal elliptical cavities 11 disposed along the longitudinal axis of the base plate. The top horizontal-surface 13 of the base block has a short dowel hole 14 in the middle and ten additional holes 15 distributed in two lines of five, each line to the side of and/equidistant from thecentral axis. The rectangular rail 20 is made of aluminum and has a shoulder projection '28 on one side and mounting flanges 22 on both sides. For aligning the rail with the base block, a dowel .pin passes through dowel hole 25 located in the middleof the lower surface of the rail and also through the dowelhole 14 located in the base block.

The base block and the railarefastened together by means of bolts passing through a line of five bolt holes 23 located on .each mounting flange .22 and through matching bolt holes 15 located in the base block- Such flanges may be extensionsof the lower portion of the rail. Shims 26 of different thicknesses placed under either side of the rail ,flanges angularly align a head supporting structure attached tothe carriage withthe', base block. In this manner,-.on alignmentonly the railflanges deflect .whilethe rail top'remains flat. Shims 26 placed between thebaseblockand the .rail are employed to .avoid'using largedeforming forces when fasteningthe -row.tolerances for smooth accurateoperation of the apparatus. For instance, the top flatness should be 0.000050 in., thesideflatness shouldbe 0.0001 in.,

and;the flatnessof the'lower surface of the shoulder projection should be 0.002 in.

In the preferred embodiment, the rail shoulder projection 28 is located along the rail, approximately in the middle of the rail side, and is slanted at an angle. This angle is the same as the angle between a horizontal line and the resultant of forces P and F, where P is the resultant of the forces exerted by the side bearing of the carriage on the rail side, and F is the resultant of the forces exerted by the top bearings of the carriage on the rail top.

Forces P and F produce steady contact of the carriage bearings on the rail and oppose external moments, for instance, those resulting from air flow on the disc pack transducer arms. Since the arm of force F is larger than that of force P, force F can be smaller than P in order to maintain the carriage in equilibrium. This conclusion indicates that the angle between a horizontal line and the resultant of forces P and F must be smaller than 45, the same as the magnitude of the angle of the lower surface of the shoulder projection. In the preferred embodiment, however, this angle has been chosen to be about 30 for symmetry and facility of manufacture.

With reference to FIGS. 2, 3, 4 and 5, the magnesium carriage 40 substantially embraces the rail with its rectangular top 41 and two triangular sides 42 and 43. At each end of the central axis of the carriage top 41, there is a slot 32 in which a bearing 33 is disposed to turn on an axle and ride on the rail top as well as share the load equally with the other bearing in the carriage top. The top of the carriage also includes two bolt holes 46 disposed along the central axis and one bolt hole 47 near each corner of the carriage rear section 48. All of these holes receive bolts to fasten the carriage to a structure 60 that supports signal transducers.

The first triangular carriage side 42 has on each corner an axle on which a bearing 34 is disposed to turn and ride on the rectangular rail side, and to share the load equally. The second carriage side 43 slants away from the rail vertical side to form a projection 54 supporting an arm 55 which carries a pre-load bearing 56 on its lower surface. This pre-load bearing 56 is disposed to ride on the lower side 29 of the rail shoulder projection 28. Arm 55 pivots about a post 57 attached to the carriage projection 54 and passing through an eccentric point in the race 58 of pre-load bearing 56. A spring 59 located in a cavity in arm 55 pushes this arm away from the carriage projection 54, thus producing a pre-loading force for bearing 56.

The arrangement of bearings on top and on the first and second sides of the carriage provide stability, rigidity and vibrationless motion to the carriage. While the bearings on vthe top 41 and on the first triangular side 42 equally share the load in their respective sides, the pre-load bearing 56 insures that all bearings ride linearly and vibrationlessly. Furthermore, the carriage having an inverted-U cross-section and embracing .a rail of simple rectangular configuration provides a combination of rail and carriage with the structural strength and rigidity of an ideal beam.

With reference to FIG. 6, bolted on to the carriage 40, there is an arm support structure 60 supporting the signal transducer, i.e. read and write heads, which transfer information signals to and from the surface of a storage magnetic disc.

The light-weight carriage 40 can be accelerated rapidly and easily controlled by an electro-magnetic actuator which includes a signal coil 61, attached to the back of the arm support structure 60, and a magnet 62. The coil moves within a cylindrical gap 63 which exists between the cylindrical center pole piece 64 and the magnet core 62. To move the carriage a current drive signal applied to the coil reacts with the magnetic field perpendicularly oriented across the gap to produce a force perpendicular to the direction of flow of the current and to the magnetic field. The'magnitude and direction of this force can be servo controlled to move the coil and, in turn, the carriage and associated signal transducers over the information storage surface of a disc in a conventional manner.

I claim:

1. Translational motion apparatus comprising:

a base;

a rectangular rail, one of the sides of the rail including a shoulder projection and the other side and the top being substantially planar, said rail being attached to the base by mounting flanges;

a symmetrical carriage having two opposed sides and a top oriented about said rail in substantially inverted-U cross-section;

a plurality of bearings disposed on said carriage with at least two bearings riding on the top of said rail and with at least three of said bearings riding on said other side of the rail and with at least one of said bearings riding on the lower surface of the shoulder projection from said rail; and

moving means for positioning the carriage along the rail.

2. A translational motion apparatus as in claim 1 wherein the mounting flanges are extensions of the lower portion of the rail, which flanges receives equally spaced screws for attachment to the base block.

3. A translational motion apparatus as in claim 1 wherein between the base block and the rail concentrate joining forces on the mounting flanges while the rail top remains flat.

4. Translational motion apparatus as in claim 2 wherein the lower surface of the rail shoulder projec tion is at an angle of approximately 45 or less with respect to a vertical line passing along the rail side opposite the shoulder projection.

5. Translational motion apparatus as in claim 4 wherein the base and rail are made of substantially the same material and the carriage is made of a light material containing magnesium.

6. Translational motion apparatus as in claim 5 wherein the inverted-U cross-section carriage included on one side of the carriage adjacent the rail shoulder projection an arm which supports a bearing in riding engagement with the lower surface of said shoulder projection.

7. Translational motion apparatus as in claim 6 wherein the bearings carried by said carriage for riding engagement with the top of said rail are disposed in slots in the top of the carriage near opposite ends thereof.

8. Translational motion apparatus as in claim 7 wherein the other side of the carriage opposite the one side thereof including the arm is substantially triangular for supporting three bearings triangularly distributed.

9. A translational motion apparatus as in claim 6 wherein the race of the pre-load bearing supported by the arm has a post passing through it at a point eccentric to the race, said post being attached to the carriage to serve as a fulcrum for the arm.

10. A translational motion apparatus as in claim 9 wherein a spring located on the end of the arm opposite to the pre-load bearing and in engagement with the arm and the carriage provides the compressive force acting on the pre-load bearing. 

1. Translational motion apparatus comprising: a base; a rectangular rail, one of the sides of the rAil including a shoulder projection and the other side and the top being substantially planar, said rail being attached to the base by mounting flanges; a symmetrical carriage having two opposed sides and a top oriented about said rail in substantially inverted-U crosssection; a plurality of bearings disposed on said carriage with at least two bearings riding on the top of said rail and with at least three of said bearings riding on said other side of the rail and with at least one of said bearings riding on the lower surface of the shoulder projection from said rail; and moving means for positioning the carriage along the rail.
 2. A translational motion apparatus as in claim 1 wherein the mounting flanges are extensions of the lower portion of the rail, which flanges receives equally spaced screws for attachment to the base block.
 3. A translational motion apparatus as in claim 1 wherein between the base block and the rail concentrate joining forces on the mounting flanges while the rail top remains flat.
 4. Translational motion apparatus as in claim 2 wherein the lower surface of the rail shoulder projection is at an angle of approximately 45* or less with respect to a vertical line passing along the rail side opposite the shoulder projection.
 5. Translational motion apparatus as in claim 4 wherein the base and rail are made of substantially the same material and the carriage is made of a light material containing magnesium.
 6. Translational motion apparatus as in claim 5 wherein the inverted-U cross-section carriage included on one side of the carriage adjacent the rail shoulder projection an arm which supports a bearing in riding engagement with the lower surface of said shoulder projection.
 7. Translational motion apparatus as in claim 6 wherein the bearings carried by said carriage for riding engagement with the top of said rail are disposed in slots in the top of the carriage near opposite ends thereof.
 8. Translational motion apparatus as in claim 7 wherein the other side of the carriage opposite the one side thereof including the arm is substantially triangular for supporting three bearings triangularly distributed.
 9. A translational motion apparatus as in claim 6 wherein the race of the pre-load bearing supported by the arm has a post passing through it at a point eccentric to the race, said post being attached to the carriage to serve as a fulcrum for the arm.
 10. A translational motion apparatus as in claim 9 wherein a spring located on the end of the arm opposite to the pre-load bearing and in engagement with the arm and the carriage provides the compressive force acting on the pre-load bearing. 